The invention is based on a fuel injection nozzle in which a fuel conduit leads via a filter body located in the nozzle housing to an injection valve at the injection ports, and a check valve which is installed in the fuel conduit and opens in the direction of fuel flow. This check valve may be provided in order to maintain a certain static pressure in the injection nozzle, so that when the injection valve closes combustion gases are prevented from reaching its valve seat and contaminating it. This could happen, for instance, in injection systems intended for small, high-speed motors in which the buildup of fuel pressure takes place very quickly following the end of injection. The check valve may additionally serve as a relief means and for receiving the positively-displaced fuel volume, thereby preventing the after-injections this fuel volume causes.
In a known injection nozzle of the type generally described above (German Pat. No. 715 51), the check valve is built into the fuel conduit directly, and the valve seat and the support surface for the closing spring are embodied on adjacent parts of the nozzle housing. This kind of embodiment makes the final assembly of the injection nozzle difficult, because additional care must then be taken that the valve elements are inserted correctly, and it may even be necessary to take measures to prevent the valve elements from falling out unintentionally from the hollow spaces provided in the nozzle housing for receiving them.